Magnetic transducer heads employing laminated assemblies of ferrite materials permit the attainment of heads having transducing gaps of very small length only with great difficulty, particularly in manufacturing. The high data recording densities required by modern-day data processing demands very narrow transducing gaps in the sensing elements as well as extremely close-flying heights of these elements relative to the magnetic recording medium (normally a high-speed spinning magnetic disc). Such desirable features are realized by fabricating a transducer head using thin film techniques and structures.
In inductively writing/magnetoresistively reading heads, such as described in the co-pending application of Jackson et al., Ser. No. 482,654, filed Apr. 4, 1983 and assigned to the instant assignee, separate circuits are required for the writing and reading functions. In more conventional heads where reading and writing are accomplished inductively only, the same circuit connections can perform both functions. Usually, in such inductively writing and reading heads, only two conductors are required to make the connections to the head since the same inductive elements perform both the writing and reading operations at different times. In a head employing magnetoresistance to read and magnetic induction to write, separate elements for each operation are utilized necessitating the use of four conductors to connect such a head to its associated circuitry, two for the magnetoresistive read elements and two for the inductive write elements.
In addition, due to the very high write currents required to operate a head which employs only a single turn for writing (as contrasted to more conventional heads utilizing eight or more turns), the conductors to the head must be substantially larger in cross-section to carry such currents. The use of a single writing turn is highly desirable in order to minimize the size and area of the transducer head structure so as to permit the attainment of higher reading and writing speeds on small diameter recording media or discs. In other words, the smaller the dimensions of the head, the more it is able to write and read compactly recorded data on the disc. This permits the use of smaller diameter discs to retain as much if not more magnetically recorded information than otherwise. For conventional heads (that is, heads which inductively write and read), utilizing a large number of writing turns, a typical writing current may be about 50 mA. For a head employing only a single turn, the writing current may be ten times that amount. This dictates the use of wires having a cross-sectional area of no more than 0.003 mm.sup.2 as compared to conventional multi-turn heads where the cross-sectional area may be 0.0008 mm.sup.2. It will be understood that wires of larger cross-sectional area become stiffer and when connected to the transducer head impair the "flying" performance thereof. The invention permits providing the necessary four conductors to the transducer head without adversely affecting its "flying" characteristics, particularly the flying height which is a critical consideration.
Due to the high writing currents and the low reading output voltages in an inductively writing/magnetoresistively reading head, the head itself should be as close as possible to an amplifier/driver integrated circuit chip. Longer wiring schemes result in excessive noise and the introduction of unacceptably high inductances and capacitances. It has been found, therefore, that the maximum permissible distance between the head and its associated amplifier/driver chip should be no more than about 25 mm.
In many disc drive applications of the type contemplated for use with inductively writing/magnetoresistively reading heads it is often desirable that at least two recording discs be vertically stacked and that each side of each disc be provided with an inductively writing/magnetoresistively reading head. Because of necessary limitations on the available spacing between such stacked discs, the connecting wiring to each head between the discs is limited in thickness. In one embodiment, the available space limits the connecting wire and the plastic film within which the wires are contained to no more than 0.2 mm. The present invention, in addition to its other advantages, permits such connections to be made within this spacing, again without adversely affecting the performance of the "flying" transducer heads.